Presentation
Accessory navicular bone - Geist classification
From the case:
Accessory navicular bone - Geist classification
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Accessory navicular bone - Geist classification
Case Discussion
The Geist1 classification divides accessory navicular bones into three types:
-
type 1 accessory navicular bone
- also known as os tibiale externum
- 2-3 mm sesamoid bone embedded within the distal portion of the posterior tibial tendon
- no cartilaginous connection to the naviculam tuberosity and may be separated from it by up to 5 mm
- accounts for 30% of accessory navicular bones
- usually asymptomatic
-
type 2 accessory navicular bone
- accounts for ~55% (range 50-60%) of all accessory navicular bones
- triangular or heart-shaped
- typically measures around 12 mm
- connected to the navicular tuberosity by a 1-2 mm thick layer of either fibrocartilage or hyaline cartilage
- eventual osseous fusion to the navicular tuberosity may take place
-
type 3 accessory navicular bone
- an especially prominent navicular tuberosity called a cornuate navicular
- thought to represent a fused type 2 and is occasionally symptomatic as a result of painful bunion formation over the bony protuberance
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